1. Field of the Invention
The present invention relates to an ink-jet cartridge containing an ink case and adapted to be used with an ink-jet printer constructed to provide a printed record of the computer output information by ejecting tiny droplets of ink onto the surface of a recording medium such as plain paper. The invention also relates to an ink-jet printer using such ink-jet cartridge.
2. Description of the Prior Art
In recent years, computers have become smaller (downsized, as we generally say), as exhibited by the development of a lap-top model replacing the desk-top model, followed by the development of a book-size or a note-size model replacing the lap-top model. With this downsizing trend in computer design, the portability and the downsizing have become major requirements for printers which are used in combination with the computers. Under these circumstances, an intense interest has been shown toward a disposable type ink-jet cartridge because this cartridge is convenient for application to the computers of lap-top size, book-size and note-size due to its noticeable usability and compactness.
FIG. 8 of the accompanying drawings shows, in exploded perspective view, the general construction of a conventional ink-jet cartridge 1.
The conventional ink-jet cartridge 1 generally comprises a housing 2 forming a body of the ink-jet cartridge 1, an ink-jet print head 3 having an ink-ejecting means composed of a plurality of nozzles (ink ejection orifices) 4 arranged in a predetermined matrix pattern, an ink-holding means or member 5 made of a porous material, such as sponge, for holding therein an ink 6 to be ejected from the nozzles 4, and an end plug 7 fitted with an open end of the housing 2 to hold the ink holding means 5 within the housing 2 under a compressed condition between the housing 2 and the end plug 7. The print head 3 further has an electric connector means 8 which supplies the print head 3 with the necessary electric energy for enabling the print head 3 to eject the ink 6 from the nozzles 4. The housing 2 has a plurality of ink flow passages 9 through which the ink 6 flows from the ink-holding means 5 to the print head 3. A filter 10 is disposed between the ink-holding means 5 and the ink flow passages 9 to remove air bubbles and a foreign matter, such as dust and dirt, when the ink 6 passes through the filter 10.
Referring now to FIG. 9, there is shown a portion of an ink-jet printer 11 including a carriage 12 in which the ink-jet cartridge 1 shown in FIG. 8 is mounted. The printer 11 also includes a wiper blade 13 made of rubber, for example, for wiping or cleaning a front surface of the print head 3 at which the front ends (discharge ends) of the respective nozzles 4 open, a blade support member 14 for supporting the wiper blade 13, a waste ink reservoir 15 for receiving and storing the waste ink, and a nozzle cap 16 for closing the nozzles 4. The wiper blade 13, blade support member 14, waste ink reservoir 15 and cap 16 are all provided on a body of the ink-jet printer 11. As shown in FIGS. 10 and 11, the printer 11 further includes a platen 17 against which a recording paper 18 is pressed by a presser plate 19. The platen 17 is rotated by a suitable drive means (not shown) in the direction of the arrow A on FIG. 11, so that the recording paper 18 is advanced in response to a rotary motion of the platen 17. In FIGS. 10 and 11, numeral 20 depicts a residual ink which remains on the front surface of the print head 3 in the vicinity of the nozzles 4 after the ejection is completed. The residual ink 20 will cause a certain problem described later on.
The conventional ink-jet cartridge 1 of the foregoing construction operates as follows.
As shown in FIG. 11, the ink 6 held in the ink-holding means 5 passes by the capillary force through the filter 10 during which time air bubbles and a foreign matter, such as dirt and dust, are removed from the ink 6. Then, the ink 6 flows from the ink flow passages 9 into the nozzles 4 in the print head 3 and reaches to the front ends of the respective nozzles 4. While keeping this condition, an electric energy is supplied to the electric connector means 8 (FIG. 8) whereupon a suitable ejection energy exerting means, such as an electric-to-thermal energy conversion element, associated with the print head 3 converts the electric energy to a thermal energy and, thereby, heats the ink 6 to such an extent as to cause a phase change which will rapidly increase the pressure of a portion of the ink 6. A sudden pressure rise thus created produces an ejection energy large enough to eject tiny droplets of ink 6 from the nozzles 4. By virtue of a negative pressure produced on ejection of the ink 6, the nozzles 4 are automatically filled with a new supply of ink 6 in the same manner as described above, thus completing preparations for the next printing operation. The ink 6 ejected from the nozzles 4 adheres to the surface of the recording paper 18 carried on the platen 17 so as to provide a printed record of information on the recording paper 18. The carriage 12 (FIG. 9) of the ink-jet printer 11 is driven to reciprocate the ink-jet cartridge 1 along the platen 17 to print an entire line at a time.
However, when the tiny droplets of ink are ejected from the nozzles 4, a very small amount of ink 6 adheres to the front surface of the print head 3 in the vicinity of the front ends of the respective nozzles 4. As the printing operation is repeated, the ink adhering to the front surface of the print head 3 grows gradually and eventually forms a mass of ink (residual ink) 20 deposited on the front surface of the print head 3. The residual ink 20 is likely to contaminate or stain the recording paper 18 and tends to change the direction of ejection of the ink 6 with the result that the printing qualities are significantly deteriorated. In addition, while the printer is not used, a volatile solvent contained in the ink 6.becomes vapor. As a result, that portion of the ink 6 held within the nozzles 4 becomes thick or sticky and hence is likely to adhere to the inside surface of the nozzles 4, thereby narrowing the nozzles 4. The nozzles 4 are, therefore, unable to eject the ink 6 with reliability and an ejection failure is thus brought about. A similar ejection failure will occur when a nozzle 4 is clogged with paper powder or any other foreign matter which is generated during printing operation.
To eliminate the foregoing difficulties (viz., the deterioration of printing qualities and the occurrence of an ejection failure caused by a substance adhering to the front surface of the print head 3 in the vicinity of the front ends of the respective nozzles 4), when either the power of the ink-jet printer 11 is turned on or off, or when the ink-Jet printer 11 completes printing operation for several sheets of recording paper 18, the carriage 12 shown in FIG. 9 is driven to traverse the ink-jet cartridge 1 along the platen 17 such that the print head 3 moves across the wiper blade 13, as shown in FIGS. 12A and 12B. With this movement of the print head 3 relative to the wiper blade 13, any substance, such as a residual ink 20, dust and dirt including paper powder remaining on the front surface of the print head 3, is wiped off or removed and then collected in the waste ink reservoir 15. Thus, the front surface of the print head 3 and the front ends of the respective nozzles 4 are cleaned. When the ink-jet printer 11 is not used, the carriage 12 is disposed in a position in which the nozzles 4 are covered by the nozzle cap 16.
The foregoing attempt of the prior art arrangement is still unsatisfactory in that since the wiper blade 13 and the waste ink reservoir 15 are disposed on the body of the ink-jet printer 11, the ink-jet printer 11 is filled up with the waste ink during a continuous use of the ink-jet printer 11. Once the waste ink reservoir 15 becomes full, a following print-head cleaning operation will result in contamination of the wiper blade 13 with a residual ink and dust and dirt. When wiped with the thus contaminated wiper blade 13, the front surface of the print head 3 is necessarily contaminated too. Most likely that the nozzles 4 are narrowed by the residual ink 20 and foreign matters, such as dirt and dust including paper powder, which adhere to the front surface of the print head 3 in the vicinity of the front ends of the respective nozzles 4. A reliable printing operation is therefore difficult to achieve and the printing qualities are deteriorated greatly. Furthermore, the cap of the nozzle is likely to catch a foreign matter, such as paper powder, during a continuous use of the ink-jet printer 11. The foreign matter will prohibit the nozzle cap from sealing the nozzles 4 perfectly. With this imperfect sealing, a volatile solvent contained in the ink 6 becomes vaporized through the nozzles 4 and, hence, that portion of the ink 6 held within the nozzles 4 becomes thick or sticky, adhering to the inside surface of the nozzles 4. Thus, the nozzles 4 again suffer from a clogging problem.